As the scales of semiconductor devices gradually decrease, extreme thin films are increasingly required. In addition, as the sizes of contact holes are reduced, limitations in step coverage are increased more and more. Thus, an atomic layer deposition (ALD) method is being used as deposition methods for addressing these limitations. In general, the ALD method is a method in which various source gases are separately supplied to a substrate to form a thin film through surface saturations of the source gases.
The principle of the ALD method will be simply described below. When a first source gas is supplied into a chamber, the first source gas reacts with a substrate surface. As a result, a monoatomic layer is chemically adsorbed onto the substrate surface. However, when the substrate surface is saturated with the first source gas, the first source gases over the monoatomic layer are physically adsorbed, but chemically adsorbed, due to non-reactivity between the same ligands. When a purge gas is supplied, the first source gases, which are physically adsorbed, are removed by the purge gas. When a second source gas is supplied on the first monoatomic layer, a second layer is grown through substitution reaction between ligands of the first and second source gases. Since the second source gases which do not react with the first layer are physically adsorbed, the second source gases are moved by the purge gas. A surface of the second layer may react with the first source gas. The above-described processes form one cycle, and then the cycle is repeated several times to form a thin film.
A related art substrate processing apparatus for performing the above-described ALD method is illustrated in FIGS. 1 and 2.
FIG. 1 is a schematic perspective view of a gas injection device in accordance with a related art. FIG. 2 is a schematic sectional view of a substrate processing apparatus, to which the gas injection device of FIG. 1 is adopted, in accordance with the related art.
Referring to FIGS. 1 and 2, a substrate processing apparatus 9 in accordance with the related art includes a chamber 1 having an inner space and a substrate support part 2, on which a plurality of substrate s are seated, rotatably installed within the chamber 1. A gas injection device 3 for supplying a gas onto the substrates s is installed at the upper portion of the chamber 1.
The gas injection device 3 is constituted by a plurality of gas injection units 4. The gas injection units 4 are spaced apart from each other by a certain angle and distance along a circumference direction. Particularly, in the constitution of the gas injection device 3, a lead plate 5 having a circular plate shape is disposed on an upper portion of the gas injection device 3, and a plurality of injection plates 6 are coupled to a lower portion of the lead plate 5. The lead plate 5 has a plurality of gas injection holes 7 arrayed about a center point thereof to inject a gas to each of the gas injection units 4 through the gas injection holes 7. A gas injected through the gas injection holes 7 is diffused between the injection plates and the lead plate and is supplied to the substrates s through gas spray holes 8 arrayed in a row in the injection plates 6.
The substrate support part 2 successively receives gases from each of the gas injection units 4 while the substrate support part 2 is rotated within the chamber 1 to perform a thin film deposition process. For example, the substrate support part 2 receives a first source gas at a time point at which the thin film deposition process starts. Then, the substrate support part 2 successively receives a purge gas, a second source gas, and a purge gas to perform the thin film deposition process.
However, there is a limitation that the substrate process apparatus 9 to which the gas injection device 3 is adopted has inconstant deposition uniformity of the thin film. That is, to uniformly deposit the thin film on the entire area of a substrate s, it may be necessary to uniformly supply a gas on the entire area of the substrate s. However, when the gas injection device 3 configured as described above is used, a large amount of gas may be supplied onto a portion of the substrate s adjacent to a central side of the substrate support part 2, and also, a small amount of gas may be supplied onto a portion of the substrate s disposed at peripheral side of the substrate support part 2, with respect to the entire area of the substrate s.
To uniformly supply a gas onto the entire area of the substrate s, it is necessary to uniformly diffuse a gas introduced through the gas injection holes 7 into a space c between the gas injection plate 6 and the lead plate 5 and discharge the gas through the gas spray holes 8. However, as depicted with arrows in FIG. 2, the gas injected through the gas injection holes 7 is not uniformly diffused into the entire region of the space c and concentrately discharged through the gas spray holes 8 disposed at the central side of the substrate support part 2.
The substrate processing apparatus 9 illustrated in FIG. 2 adopts a so-called side pumping type in which a pumping passage P is disposed the outside thereof. Thus, since the gas injection holes 7 are forced to be defined in the central side of the gas injection device 3, the gas is not sufficiently diffused into the inside of the gas injection device 3 due to a pressure difference between the inside of the chamber 1 and the inside of the gas injection device 3.
Furthermore, since the substrate support part 2 performs the thin film deposition process while being rotated, the peripheral side of the substrate support part 2 is rotated by a distance greater than that by which the central side of the substrate support 2 is rotated, for the same time. Thus, even though the gas is uniformly supplied into the entire area, the amount of gas supplied to the peripheral side of the substrate support part 2 for the same time may be decreased.
Thus, the portion of the substrate s disposed at the peripheral side of the substrate support part 2 and the portion of the substrate s disposed at the central side of the substrate support part 2 within the one substrate s may be deposited at thicknesses different from each other.